nice what that mount on a cz?
Yep, non-restricted CZ 858-2 Tactical. Great match having a non-restricted M203 on there cause you can still take it hunting

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As far as explosive rounds, etc, you're pretty limited.
Here are your choices:
1. You
CAN NOT use any round that
IS DESIGNED TO ignite or explode on
IMPACT, they are illegal.
2. You can shoot 12ga "bear bangers" (explosive class = consumer, 1.4g) using a 40mm to 12ga adapter (legallity of this adapter is questionable if used in a 37mm launcher).
Click for manufactures site,
click for video of me shooting one. They are designed to explode after time delay (approx 1 second).
3. You can make your own binary compound explosive rounds if you have the proper license:
http://www.nrcan.gc.ca/mms/explosif/edu/edu_e.htm , click under Education, Pyrotechnic Special Effects Course. Costs $100 and as soon as your done the 1 day course, you can buy flash powder and manufacture your own explosive rounds (explosive class = professional, 1.3g). Only YOU can light them off, you can't sell or lend them or anything. There are special storage requirements (can't store em in your house, has to be seperate detached building on your property. Can't carry more then 25kg of them at a time in your car, etc.) Only you are licensed to manufacture them and use them. Remember, must be time delay fuse.
There are a couple of more options which I'm in the process of trying, but it doesn't look promising. The ERD just moved a bunch of the "fun stuff" to explosives class 1.1, which is the evil class. Can't move it in your car, need seperate storage bunker, pretty damn sure they wouldn't let you shoot it outa the launcher, etc.
In the videos I am using a 40mm to 1" aluminum adapter I had a machine shop make, cost about $35 for the material (6061 T6) and time. It uses a W209 shotgun primer, and is easily reloadable.
In the videos I'm shooting (inert) 1" dia x 2" oak dowel peices, on top of 130grains of FFFFg (yes, that's four f's) black powder.
Here is a good video showing the adapter up close:

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Of course the 12ga flare rounds are no problem. I've never seen any comercially available 40mm or 37mm flare rounds. And of course, any inert chalk round, plastic round, etc, no problem.